1. Field of the Invention
The present invention relates to hoist hooks. More particularly, the present invention relates to a device for remotely actuating the safety latch associated with a crane or hoist hook.
2. Description of the Prior Art
Crane and hoist hooks typically include a safety latch which closes the hook opening to prevent the load supported by the hook from accidentally coming off the hook. The safety latch is normally biased across the hook opening by a latch spring to prevent disengagement of the load from the hook, particularly in the event the hook line goes slack due to the load colliding with another surface. The hook, however, must eventually be released from the load after the load is positioned on the proper surface and, when this surface is not readily accessible, release of the hook becomes difficult. This is particularly true in the construction of large buildings, where reaching the hook to manually disengage the safety latch can often be dangerous and time consuming.
As a result, many workers tie back the safety latch on the hook so that the hook remains open, thereby eliminating the need to manually release the hook once it is properly positioned. This practice is known in the trade as "mousing the latch". Tying the safety latch back violates many safety regulations and is a dangerous and unsafe practice.
Devices for remotely actuating the safety latch of crane and hoist hooks are known in the art. Examples of such devices are seen in U.S. Pat. No. 4,195,872, issued to Clifford I. Skaalen on Apr. 1, 1980, and U.S. Pat. No. 5,108,139, issued to Kenneth E. Leech on Apr. 28, 1992. Skaalen shows a safety latch operating device having a tension cable swivelly attached to the safety latch. The cable extends through a hole in the shank of the hook and is connected to a tag line for remote operation of the safety latch. Leech shows a safety latch operating device having an L-shaped latch which is attached to the hook and which carries a pulley for supporting a cable adapted to attach to the safety latch. The cable attaches to a rope for remote actuation of the safety latch. Both Skaalen and Leech require at least two people to operate the safety latch of the hook--one person to control the movement of the hook, typically from within the crane cab, and one person to operate the cable controlling the safety latch. Also, the person operating the cable is often required to stand in a dangerous location--below the load being lifted by the hoist hook. For these reasons, there is a need for a device which will enable the operators of cranes and hoists to automatically open and close the safety latch on their hook.
Pneumatically and hydraulically operated hoist hooks are well known in the art. Examples of such hooks are seen in U.S. Pat. No. 4,077,661, issued to Kiichiro Inchashi on Mar. 7, 1978; U.S. Pat. No. 4,095,833, issued to Charles B. Lewis on Jun. 20, 1978; U.S. Pat. No. 4,185,864, issued to Lawrence M. Phillips on Jan. 29, 1980; U.S. Pat. No. 4,416,480, issued to Jack M. Moody on Nov. 22, 1983; and U.S. Pat. No. 5,178,427, issued to Johannes N. Jorritsma on Jan. 12, 1993. None of the above referenced teach or suggest an automatic crane hook safety latch having an actuating means controlled by a command signal from a transmitter.
U.S. Pat. No. 3,259,419, issued to Henry E. Schwarzbach on Jul. 5, 1966, shows a releasable hoist hook having a remotely controlled release means for automatically removing the load from the hook. The release means may be electrical, hydraulic, pneumatic, or mechanical. To activate the release means, an insulated coil extends from the hook to the remote control station. The hook taught in Schwarzbach lacks a safety-latch biased across the hook opening by a latch spring to prevent disengagement of the load from the hook. Also, Schwarzbach does not teach or suggest an automatic crane hook safety latch having an actuating means controlled by a command signal from a transmitter.
U.S. Pat. No. 4,149,746, issued to Edward C. Androski on Apr. 17, 1979, shows a remote-controlled safety hook assembly. The hook taught in Androski also lacks a safety-latch biased across the hook opening by a latch spring to prevent disengagement of the load from the hook. In addition, Androski also does not teach or suggest an automatic crane hook safety latch having an actuating means controlled by a command signal from a transmitter.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.